This invention relates broadly to wastewater management, and more specifically to level control devices used in wastewater pump stations. Wastewater is generated from common sources, such as homes, schools, restaurants, hotels, office buildings, and the like. From these sources, wastewater enters a collection system and is gravity fed downstream through underground sewer pipes to a municipal treatment plant where the wastewater is chemically and biologically treated for return to the environment. Collection basins containing one or more wastewater pumps are located in areas of low elevation between the sources of wastewater and the treatment plant.
A pump station is generally constructed of concrete or fiberglass, and is typically between 4 to 12 feet in diameter and can range from 4 to over 40 feet deep. The pump station receives the flow of wastewater from the gravity sewer pipes that feed it. The pump station also houses one or more discharge pumps that serve to xe2x80x9cpushxe2x80x9d the wastewater to another high point, or directly to the treatment plant. Depending on the plant location, multiple pump stations may be required to transport the wastewater to its final destination for treatment.
Each pump station has some means of signaling when the discharge pumps should turn xe2x80x9conxe2x80x9d and xe2x80x9coffxe2x80x9d depending on the level of wastewater in the basin. Most commonly, this signaling means includes four float switches staggered at different elevations in the basin. These floats are wired back to a central control panel that houses the motor starters for the pumps. Depending on which of the floats xe2x80x9ctipxe2x80x9d determines which of the pump motors energize, when they xe2x80x9cdeenergize,xe2x80x9d and when there is a xe2x80x9chigh waterxe2x80x9d or xe2x80x9clow waterxe2x80x9d condition.
Wastewater entering these pump stations is composed of many ingredients besides water-the most common being various forms of grease. As wastewater stored in the pump station becomes stagnant, most of this grease rises to the surface and solidifies. This grease tends to collect on, and build-up around, anything it touches. It is particularly common for grease to collect on the aforementioned floats that control the operation of the pumps. When grease collects on a float, it generally weighs the float down. It commonly restricts the operation of the electrical switch which controls automatic operation of the pump by not allowing the float to xe2x80x9ctipxe2x80x9d. In this case, the pump motor can not activate to transfer the rising wastewater from the pump station further downstream towards the treatment plant. As a result, the station goes into an xe2x80x9calarmxe2x80x9d state, and can overflow onto the ground around it, and into a nearby creek or stream. In other instances, grease will xe2x80x9cbridgexe2x80x9d from a float to a pipe or other structure in the pump station, and the float will xe2x80x9cstickxe2x80x9d in the xe2x80x9cupxe2x80x9d position. When this happens, the pump motor never gets its signal to turn off, and continues to run even after there is no wastewater remaining in the basin. In this event, the motor overheats causing substantial and costly mechanical damage to the pump.
The present invention addresses these concerns by replacing the traditional buoyant float with a buoyant float having an anti-accumulation surface that will resist the accumulation of grease and other waste. In one embodiment of the invention, the surface of the float is heated using an electric current. Alternatively, the surface of the float may be coated with an anti-friction material, such as Teflon.
Therefore, it is an object of the invention to provide a level control device for a wastewater pump station which cooperates with the discharge pump(s) to manage the volume of wastewater contained in the basin.
It is another object of the invention to provide a level control device which includes a buoyant housing that resists accumulation of grease and waste.
It is another object of the invention to provide a level control device which operates properly over an extended period of usage with little maintenance and cleaning.
These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing a level control device adapted for use in a wastewater pump station. The level control device cooperates with a discharge pump to control the volume of wastewater contained in the basin. The level control device includes a buoyant housing for being located in the basin, and capable of floating on a surface of the wastewater. Anti-accumulation means acts to resist accumulation of grease and other waste on the surface of the housing.
According to another preferred embodiment of the invention, the buoyant housing has a conductive surface for receiving and transmitting heat to the immediate surrounding area. This anti-accumulation means includes a heating element connected to the housing to heat the conductive surface such that grease, and other waste contained in the basin, resists adhering to the heated surface.
According to another preferred embodiment of the invention, the heating element includes an electrode designed to carry an electric current from an electrical source to the conductive surface of the housing.
According to another preferred embodiment of the invention, the electrode is a copper wire.
According to another preferred embodiment of the invention, the conductive surface of the housing is stainless steel.
According to another preferred embodiment of the invention, a power cable is attached to the housing and may include a plug for being inserted into an electric outlet.
According to another preferred embodiment of the invention, a weight is secured to the power cable to suspend the float at the desired elevation.
According to another preferred embodiment of the invention, the control switch includes a mercury control switch or a mechanical switch contained in the housing.
In another embodiment, the invention is a method for controlling the volume of wastewater contained in a wastewater pump station. The method includes the steps of employing a discharge pump for removing wastewater from the basin. A buoyant float switch is positioned in the basin, and capable of floating on a surface of the wastewater. Anti-accumulation means are provided for resisting accumulation of grease and other waste on the surface of the housing. The float is wired through the pump control panel, which is wired to the discharge pump, to activate the pump when the float xe2x80x9ctipsxe2x80x9d at a predetermined elevation in the basin triggered by the increasing level of wastewater.